#!/usr/bin/env python
"""Cherry pick and backport a PR"""

import sys
import argparse
from os.path import expanduser
import re
from subprocess import check_call, call, check_output
import requests

usage = """
Example usage:

./dev-tools/cherrypick_pr --create_pr 5.0 2565 6490604aa0cf7fa61932a90700e6ca988fc8a527

In case of backporting errors, fix them, then run:

git cherry-pick --continue
./dev-tools/cherrypick_pr --create_pr 5.0 2565 6490604aa0cf7fa61932a90700e6ca988fc8a527 --continue

This script does the following:

* cleanups both from_branch and to_branch (warning: drops local changes)
* creates a temporary branch named something like "branch_2565"
* calls the git cherry-pick command in this branch
* after fixing the merge errors (if needed), pushes the branch to your
  remote
* if the --create_pr flag is used, it uses the GitHub API to create the PR
  for you. Note that this requires you to have a Github token with the
  public_repo scope in the `~/.elastic/github.token` file

Note that you need to take the commit hashes from `git log` on the
from_branch, copying the IDs from Github doesn't work in case we squashed the
PR.
"""


def main():
    """Main"""
    parser = argparse.ArgumentParser(
        description="Creates a PR for merging two branches",
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog=usage)
    parser.add_argument("to_branch",
                        help="To branch (e.g 5.0)")
    parser.add_argument("pr_number",
                        help="The PR number being merged (e.g. 2345)")
    parser.add_argument("commit_hashes", metavar="hash", nargs="+",
                        help="The commit hashes to cherry pick." +
                        " You can specify multiple.")
    parser.add_argument("--yes", action="store_true",
                        help="Assume yes. Warning: discards local changes.")
    parser.add_argument("--continue", action="store_true",
                        help="Continue after fixing merging errors.")
    parser.add_argument("--from_branch", default="master",
                        help="From branch")
    parser.add_argument("--create_pr", action="store_true",
                        help="Create a PR using the Github API " +
                        "(requires token in ~/.elastic/github.token)")
    args = parser.parse_args()

    print(args)

    tmp_branch = "backport_{}_{}".format(args.pr_number, args.to_branch)

    if not vars(args)["continue"]:
        if not args.yes and raw_input("This will destroy all local changes. " +
                                      "Continue? [y/n]: ") != "y":
            return 1
        check_call("git reset --hard", shell=True)
        check_call("git clean -df", shell=True)
        check_call("git fetch", shell=True)

        check_call("git checkout {}".format(args.from_branch), shell=True)
        check_call("git pull", shell=True)

        check_call("git checkout {}".format(args.to_branch), shell=True)
        check_call("git pull", shell=True)

        call("git branch -D {} > /dev/null".format(tmp_branch), shell=True)
        check_call("git checkout -b {}".format(tmp_branch), shell=True)
        if call("git cherry-pick -x {}".format(" ".join(args.commit_hashes)),
                shell=True) != 0:
            print("Looks like you have cherry-pick errors.")
            print("Fix them, then run: ")
            print("    git cherry-pick --continue")
            print("    {} --continue".format(" ".join(sys.argv)))
            return 1

    if len(check_output("git status -s", shell=True).strip()) > 0:
        print("Looks like you have uncommitted changes." +
              " Please execute first: git cherry-pick --continue")
        return 1

    if len(check_output("git log HEAD...{}".format(args.to_branch),
                        shell=True).strip()) == 0:
        print("No commit to push")
        return 1

    print("Ready to push branch.")
    remote = raw_input("To which remote should I push? (your fork): ")
    call("git push {} :{} > /dev/null".format(remote, tmp_branch),
         shell=True)
    check_call("git push --set-upstream {} {}"
               .format(remote, tmp_branch), shell=True)
    if not args.create_pr:
        print("Done. Open PR by following this URL: \n\t" +
              "https://github.com/elastic/beats/compare/{}...{}:{}?expand=1"
              .format(args.to_branch, remote, tmp_branch))
    else:
        token = open(expanduser("~/.elastic/github.token"), "r").read().strip()
        base = "https://api.github.com/repos/elastic/beats"
        session = requests.Session()
        session.headers.update({"Authorization": "token " + token})

        original_pr = session.get(base + "/pulls/" + args.pr_number).json()

        # get the github username from the remote where we pushed
        remote_url = check_output("git remote get-url {}".format(remote),
                                  shell=True)
        remote_user = re.search("github.com:(.+)/beats", remote_url).group(1)

        # create PR
        request = session.post(base + "/pulls", json=dict(
            title="Cherry-pick #{} to {}: {}".format(args.pr_number, args.to_branch, original_pr["title"]),
            head=remote_user + ":" + tmp_branch,
            base=args.to_branch,
            body="Cherry-pick of PR #{} to {} branch. Original message: \n\n{}"
            .format(args.pr_number, args.to_branch, original_pr["body"])
        ))
        if request.status_code > 299:
            print("Creating PR failed: {}".format(request.json()))
            sys.exit(1)
        new_pr = request.json()

        # add labels
        session.post(
            base + "/issues/{}/labels".format(new_pr["number"]), json=["backport", "review"])

        # remove needs backport label from the original PR
        session.delete(base + "/issues/{}/labels/needs_backport".format(args.pr_number))

        print("\nDone. PR created: {}".format(new_pr["html_url"]))
        print("Please go and check it and add the review tags")


if __name__ == "__main__":
    sys.exit(main())
